In recent years, lubricating oil compositions used as driving system oils, such as automatic transmission fluids (ATF), continuously variable transmission fluids (CVTF), and shock absorber fluids (SAF), engine oils, hydraulic fluids, and the like have been required to have various characteristics according to various applications.
Since characteristics of a lubricating oil composition often largely depend on the nature of a base oil used therein, development of such a base oil that can produce a lubricating oil composition capable of exhibiting required characteristics has been actively promoted.
For example, PTL 1 discloses a hydrocarbon lubricant base oil having a flash point of 170° C. or higher, a kinematic viscosity at 40° C. of 9.0 to 14.0 mm2/s, a viscosity index of 100 or more, a 6 volume percent distillation temperature in a distillation test of 310° C. or higher, a pour point of −30° C. or lower, and an aromatic content (% CA) of 0.1 or less.
According to the disclosure of PTL 1, the lubricant base oil is suitable for lubricating oil compositions used at high temperature, such as power steering fluids and transmission fluids for automobiles, since the lubricant base oil has a high flash point while maintaining a viscosity a conventional lubricant base oil has.